1. Field of the invention
The invention relates to a device for sealing a turbomachine bearing chamber.
Conventionally a turbomachine bearing assembly supporting a shaft which rotates within a fixed casing comprises a rolling bearing disposed in a chamber enabling it to be lubricated. However, oil migration to certain compartments of the turbomachine must be avoided and a seal is therefore necessary at the separation between the oil-containing bearing chamber and an adjacent air chamber which must be kept oil-free.
2. Summary of the prior art
Various solutions to this problem have been proposed. For example, labyrinth seals have been used and have the advantage of being simple to manufacture and of having a long working life. However, they may give rise to substantial air leakage, which impairs performance, and untrue running of the shaft may cause damage. There is therefore an increase in the amount of oil carried by the air to the air-oil separator and it is possible for oil to leak from the oil chamber into the air chamber.
Other solutions to the problem use carbon seals which can be positioned in various ways. In particular, EP-A-0387122 discloses one example of a segmented radial seal, and EP-A-0562895 discloses another example. The use of contact seals greatly reduces air leakage into the oil chamber and, in consequence, the oil consumption after passage through an oil separator. However, the effects of untrue running of the shaft are not overcome and there is considerable friction causing wear, so that seals of this kind have a limited working life which is often of the order of a thousand hours and inadequate for the uses intended for this invention.